Engine/Transmission (1998.5 - 2002) What Comp settings for EZ performance?

[Gary - K7GLD]

Here's the text of a message I sent directly to Edge - but while they make great products, they are LOUSY at responding to email! So, I wonder if any here have some pretty well founded info to offer on my letter posted below?



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I have had your Comp on my '02 2500 Dodge HO for several years with EXCELLENT performance, especially when towing our 5th wheel RV in the mountains.



I recently added larger injectors (Don M 1. 6's), and a BHAF and full Rip Rook 4 inch exhaust system.



I find that now I rarely need the Comp on at all for most situations, expecially in regards to added fueling - but it IS nice to have there for those rare "extra" need situations. I feel that the TIMING change provided by the Comp might sometimes be useful, IF the additional fueling could be prevented along with it. As I undestand it, the Comp DEfuels in the lower ranges 1-3 when the sub menu is set below 3, such as 1x1. How is this accomplished, is only the ADDED Comp fueling reduced or eliminated - or is the TOTAL injection pump flow reduced? I *do* see lots less smoke with the Comp on 1x1 than I do with it switched completely off with my added injectors.



Is it possible to connect the Comp normally, and still have it function essentially like your EZ, as long as only the lower settings are used, or must I disconnect the pump wire for that to happen? I'd really like to keep it connected normally to have full power available at the touch of a button, but might consider disconnecting the pump wire if that is the only way this can happen.



Thanks for your help

 

[mgoncalves]

As I undestand it, the Comp DEfuels in the lower ranges 1-3 when the sub menu is set below 3, such as 1x1. How is this accomplished, is only the ADDED Comp fueling reduced or eliminated - or is the TOTAL injection pump flow reduced?

Gary,



The comp's sublevels are basically an adjustable boost fooler. The ECM will only give X amount of fuel with X amount of boost, like an aneroid. What the comp does in the lower sublevels is give a false signal saying there is not as much boost as there really is. For example, if you are making 10 psi, sublevel one would only let the ECM see 2 psi, so the ecm is only giving enough fuel for 2 psi but you're burning it with 10 psi, causing little to no smoke.



On the flipside, sub level 5 would show the ecm 10 psi when you are only making 2 psi. The ecm fuels 10 psi worth, and you get lots of smoke before you build any boost.



Sub Levels 2-4 are just different points between 1 and 5, with level 3 being the closest to stock.



Make sense



Matt

 

[Scrappy]

Leave it on 1X and the pump wire doesn't do anything, I believe anything over that the wire comes into play.

 

[mgoncalves]

Is it possible to connect the Comp normally, and still have it function essentially like your EZ, as long as only the lower settings are used, or must I disconnect the pump wire for that to happen?

Absolutely, if you stay on power level one, it does not send any voltage through the pump wire, and is functioning as an EZ.



I used to drive on 1x1, and hit 5x5 for fun every once in a while. Remember, you set the sublevels for each power level separetly and they stay the way you set them for each power level until you change them.





Matt

 

[Gary - K7GLD]

Absolutely, if you stay on power level one, it does not send any voltage through the pump wire, and is functioning as an EZ.



I used to drive on 1x1, and hit 5x5 for fun every once in a while. Remember, you set the sublevels for each power level separetly and they stay the way you set them for each power level until you change them.





Matt

ONE of my main concerns, is avoiding the added (and at this point unnecessary!) stress on the VP-44 by forcing it into the added second fuel injection event it is designed to provide after the first stock injection event. I suspect, as do some others, the essentially DOUBLING the work load of the VP-44 this creates potentially shortens it's life span, and with the upgraded injectors, that added stress is not needed.



If I didn't already have the Comp installed, I would probably have an EZ instead - but of course, the Comp IS still valued for the upper level power it can provide in rarer instances.



From what both you fellas are saying, the ONLY Comp level that sorta duplicates the non-fueling EZ, is in level one - if so, I guess that's the highest level I will use, unless a "Banzai" run is called for!



Thanks.

 

[darkhorse]

ONE of my main concerns, is avoiding the added (and at this point unnecessary!) stress on the VP-44 by forcing it into the added second fuel injection event it is designed to provide after the first stock injection event.



Gary, I don't think that is quite right. The signal in the wire to the pump holds the fuel bypass valve closed a little longer & thereby lengthening the injection event, not creating a second one. On level 1 the comp will act like the EZ but with the added advantage of the sub levels. Now I believe that an EZ on the middle jumper will perform like the Comp set on 1X3. I hope I have that right. If not, perhaps some one with some real knowledge on the topic will chime in.

 

[Gary - K7GLD]

Marco in Italy, developer of the MAD ECM has posted several times that the fueling function of the Comp is that it operates by adding a second fuel injection immediately after the first stock event of the VP-44, and that is what I refer to - I assume he is correct, he has spent a lot of time researching these various aftermarket boxes, and their operation as part of his development of his ECM reprogramming.



Here's one of his quotes in response to that subject:



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What Marco means is that when you have a major fueling box on your truck that taps the pump wire, it detects when your ECM send a signal to the VP-44 to start injecting fuel and the fueling box then adds on to that signal making the injection event longer, giving more fuel and thus making more power.

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Nope that's not the way the "major" fuelling boxes work.

The boxes that tap the pump wire do add an SECOND injection stroke after the ECM's one.



It works like this:

The ECM sends it's signal to the VP. The VP executes that command and injects the requested fuel with the requested timing by the ECM. The box adds then ANOTHER injection stroke AFTER the "main" injection stroke from the ECM. That's possible because the VP's have been designed for TWO injection strokes by Bosch from the beginning. The major fuelling boxes do "activate" an function that's already there but has not been used by Cummins. That can be easily seen hooking up a scope to the pump wire...



Clear as mud?



From the above it's also clear that:

1) Those boxes add fuel with a retarted timing ( the second stroke takes place later )

2) The EGT's will raise to abnormal levels ( late timing and more fuel )

3) These boxes sqeeze out as much fuel as the VP has in the plungers...

 

[darkhorse]

That's an instructive clip from Marco. Thanks Gary. Apparently I'm not the only one to be mistaken in that regard. Still, I don't think that second stroke is a problem for the VP44. Of more concern is the extra heat rise with the elongated "double" injection event.